This invention relates to a charging device for automatic copying apparatus of the type which comprises charging wires arranged in a charger case, and a charging circuit for supplying a charge voltage to the charging wires.
Increased industrial activities have in recent years brought about a marked increase in the amount of information handled within a business unit or between business units. This has created a demand for copying apparatus capable of operating at increased speed in connection with propagation of information carried out by using paper as a medium of communication.
In automatic copying apparatus commercially available nowadays, the charging device used as means for charging the surface of a photoconductor usually operates such that charging is effected intermittently in preparation for imagewise exposure to radiation of the photoconductor. This requires the provision of a relatively complex circuit. At the same time, there is the problem of difficulty being encountered in accomplishing instantaneous actuation of the charging device when charging is to be performed. This problem is raised because it is impossible to reduce beyond a certain limit the time interval for the charging wires to respond to ON and OFF signals due to electrical inertia, hysteresis and energization of the charger. Thus, intermittent charging has hitherto been one of the factors concerned in hampering realization of high speed document copying. To obviate the above-described disadvantages of the prior art, proposals have been made to perform charging continuously and remove by means of a lamp, immediately before the exposed photoconductor is introduced into the developing station, the unnecessary charge carried by the non-image region which was not discharged at the time the photoconductor was exposed to an optical image of an original. This system has disadvantages in that a mechanism of complex construction is required which occupies more space than the usual system and that the residual potential is high.